Quaternary ammonium compounds represent an important class of cationic surface-active agents which are used in a variety of commercial products. Quaternary ammonium compounds have a positively charged nitrogen atom and at least one hydrophobic long-chain substituent in the molecule. Quaternary ammonium compounds are exemplified by the structure: ##STR1## where R.sub.1 is a substituted or unsubstituted alkyl or aryl group having about 6 to 24 carbons; R.sub.2 is an alkyl, aryl or arylalkyl group having about 6 to 24 carbons; R.sub.3 and R.sub.4 represent alkyl groups having 1 to 4 carbons; and X represents an anion consisting of either a halide salt, sulfate, carbonate, acetate, and nitrate. Exemplary quaternary ammonium compounds are generally classified as monoalkyltrimethyl ammonium salts, monoalkyldimethylbenzyl ammonium salts, and dialkyldimethyl ammonium salts.
Quaternary ammonium compounds have an extremely strong affinity for negatively charged substrates. Their highly adsorptive properties make them suitable for a wide variety of commercial applications. For example, these compounds are utilized as fabric softeners, laundry detergents, anti-static sprays, flotation promoters for the mining industry, asphalt and petroleum additives, in the manufacturing of organo-modified clays (used in drilling muds). Other major uses include corrosion inhibitors and highly potent germicides/deodorizers, and biocides.
Through their intended uses, quaternary ammonium compounds ultimately end up in the aquatic environment. A majority of these compounds enter wastewater treatment facilities where they are removed or reduced by numerous mechanisms including adsorption, complexation and biodegradation to levels non-toxic to aquatic life upon their discharge to the environment. However, the uses of quaternary ammonium compounds as biocides particularly for controlling biological fouling or as corrosion inhibitors in industrial cooling water systems are often not sent to a wastewater treatment facility but are released directly to the aquatic environment. The discharge water streams from industrial cooling water systems and other aqueous systems treated by such quaternary ammonium based compounds may contain elevated residual amounts. Such releases may cause unacceptable shod-term or long-term impacts to aquatic life within the receiving stream. Aquatic life referred to herein includes microbiological organisms (i.e., bacteria, fungi, and algae), fish, planktonic and benthic macroinvertebrates, and zooplankton assemblages living within streams, rivers, lakes, reservoirs, estuaries, and oceans. Quaternary ammonium compounds may be acutely toxic to specific aquatic organisms at concentrations as low as 10 ug/L.
Concerns with respect to such discharge of quaternary ammonium compounds and other toxic waste products into the aquatic environment has grown significantly in recent years. This growing concern is manifested, in part, in the actions of municipal, state and federal environmental regulatory authorities who have either already enacted legislation to eliminate the pollution of our natural waters or who are in the process of promulgating such regulations. The regulations and legislation enacted by such authorities are becoming more and more stringent with the ultimate goal being the prohibition of the addition of any chemical compound into the aquatic environment which has even an insignificant effect on the aquatic life which exists therein.
In response to such legislation, industrial users of large volumes of water have sought out methods of decreasing effluent toxicity. For example, U.S. Pat. No. 3,524,812 teaches a method of decreasing the biocidal effects of bromonitrostyrene by reaction with a compound selected from a water soluble sulfite compound, hydrogen peroxide, and potassium permanganate. U.S. Pat. No. 4,204,954 teaches the use of anionic substances such as sodium stearate, sodium dodecylsulfate, dodecylglycine, dodecylaminoethylglycine, sodium palmitate, sodium oleate, sodium linoleate, and sodium dioctylsulfosuccinate to detoxify quaternary ammonium based biocides.
The addition of clays to water treated with quaternary ammonium based biocides prior to release into the environment is known. Such materials, particularly bentonite clays, have been shown in laboratory and field tests to be effective at detoxifying quaternary ammonium based biocides. While clays have been shown to be effective treatments for the detoxification of biocides, they are troublesome to feed. U.S. Pat. No. 5,169,536 teaches a method of detoxifying cationic surfactant based biocides with a combination of bentonite clay detoxification agent and a polymerized alkyl naphthalene sulfonate sodium salt dispersing agent. While clay based detoxification methods are effective, regulatory agencies have shown concern over the long term deposition and accumulation of inert clays and their environmental impact.